The PowerShares QQQ Trust, Series 1 (ETF) (NASDAQ: QQQ) and the corresponding index are on track to accomplish something that hasn't been seen in decades.

According to data compiled by Bespoke Investment Group, the Nasdaq index closed higher 16 of 19 days in May. The current pace implies the index on track to become the winningest month going back all the way to September 1996.

Will the index hold on to break a multi-decade long record or should investors be trimming positions amid the strong gains? This was the focus of discussion on a CNBC "Trading Nation" segment, which featured BK Asset Management's Boris Schlossberg.

According to Schlossberg, investors should keep in mind that the large concentration of positive days typically implies a mean reversion is "about to kick in." As such, the "sell in May" slogan might be prudent as investors could sell some of their positions at peak levels and look to re-enter when the market is ready to "re-rally" perhaps in September or November.

Is Today The Same As 1996?

Back in 1996 when the Nasdaq was just getting started and the bull rally carried over for years until peaking at the dot.com bubble. So, is today any different from 1996?

Schlossberg argued that the Nasdaq index has already experienced a strong gain over the years, and today's environment is void of the "pure mania" that dominated stocks in the 1990s.

At the end of the day, the surge in the Nasdaq index and the rise of American tech companies to become global behemoths is a story that has been "really well told" by now.

"I think profit-taking is due here, and I would be very cautious at trying to get long here at these levels," Schlossberg concluded.